eldo_user

Post-Layout Simulation
Reduction Output
The NOISE_ERROR parameter is defined as the amount of change in noise amplitude relative
to a full-strength signal. The noise-error value is a ratio, a unitless floating number. The default
value is 0.01 (corresponding to 1%) for the .REDUCE ANALOG=YES command and 0.05
(5%) for the .REDUCE ANALOG=NO command. Default values for both .REDUCE
ANALOG=YES and .REDUCE ANALOG=NO commands are denoted analog default values
and digital-like default values respectively.
The DELAY_ERROR parameter refers to the timing delay threshold used for reduction. The
delay error units are seconds. The analog default is 0.5e-12 (a half picosecond); the digital-like
default is 1.0e-12 (one picosecond).
The FREQUENCY parameter (cut-off frequency) refers to the upper limit of the frequency
band ranging from DC upwards, over which the Eldo Reduction is requested to maintain
accuracy of the simulation results computed using the reduced circuit, within the effective noise
error and delay error margins, as compared to the simulation results that would be obtained with
the original unreduced circuit. Refer to the “.REDUCE” command in the Eldo Reference
Manual for a more detailed explanation of this cut-off frequency parameter.
Since the members of this parameter trio are interdependent, at most two of them can be
specified. Moreover, some of them—even if specified explicitly on the reduction command—
may be overridden according to parameters specified on some possibly conflicting reduction
commands, according to the minimum frequency required to resolve the circuit input signals
and possibly to the frequency range implied by the required simulation analyses as well. When
such a situation occurs, Eldo issues a warning indicating the effective value of the reduction
parameter being modified.
See Also
• .REDUCE in the Eldo Reference Manual
• Reduction Options in the Eldo Reference Manual
Reduction Output
Statistics are printed to enable you to assess the efficiency of the reduction process using the
default or specified parameter values (noise error, delay error, and/or cut-off frequency).
These statistics may change between two successive Eldo versions as a result of a permanent
development process toward increasing reduction efficiency. Nevertheless, the accuracy of the
simulation results, relative to those of the original unreduced circuit, is preserved as long as the
reduction cut-off frequency, noise error, and delay error are set adequately.
See Also
• Reduction Options in the Eldo Reference Manual.
Eldo® User's Manual, 15.3 405